Stability of Steady Multi-Wave Configurations for the Full Euler Equations of Compressible Fluid Flow

We are concerned with the stability of steady multi-wave configurations for the full Euler equations of compressible fluid flow. In this paper, we focus on the stability of steady four-wave configurations that are the solutions of the Riemann problem in the flow direction, consisting of two shocks, one vortex sheet, and one entropy wave, which is one of the core multi-wave configurations for the two-dimensional Euler equations. It is proved that such steady four-wave configurations in supersonic flow are stable in structure globally, even under the BV perturbation of the incoming flow in the flow direction. In order to achieve this, we first formulate the problem as the Cauchy problem (initial value problem) in the flow direction, and then develop a modified Glimm difference scheme and identify a Glimm-type functional to obtain the required BV estimates by tracing the interactions not only between the strong shocks and weak waves, but also between the strong vortex sheet/entropy wave and weak waves. The key feature of the Euler equations is that the reflection coefficient is always less than 1, when a weak wave of different family interacts with the strong vortex sheet/entropy wave or the shock wave, which is crucial to guarantee that the Glimm functional is decreasing. Then these estimates are employed to establish the convergence of the approximate solutions to a global entropy solution, close to the background solution of steady four-wave configuration.Comment: 9 figures

Environmental and Trophic Factors that Influence the Prevalence of Gonionemus vertens in the Northeastern United States

Gonionemus vertens, often referred to as the clinging jellyfish, is an invasive hydrozoan first documented in 2016 in New Jersey. Populations of the adult medusa stage bloom in May and continue to persist through the middle of July, during which time it is of particular concern from a public health standpoint. G. vertens \u27clings\u27 to sea grasses and other submerged aquatic vegetation in shallow coastal waters, which are highly utilized for recreational activities, and its sting is highly toxic, which can hospitalize victims for days with both physical and psychiatric symptoms. Encounters with highly toxic G. vertens are, unfortunately, becoming more frequent in areas such as the estuaries of Barnegat Bay, New Jersey and Potter Pond, Rhode Island; which could be a deterrent to those visiting popular beaches and shoals for recreational purposes. Laboratory experiments and field observations demonstrate that several factors seem to contribute to the cessation of bloom conditions such as top-down pressure by sea nettles, water temperatures exceeding 28° C, or a combination of both. Medusae were collected from various locations in Barnegat Bay and Potter Pond during several field surveys in the summers of 2018 and 2019, as well as from Cape May, NJ and Mumford Cove, CT in 2019. Medusae were maintained in holding tanks in the laboratory under stable temperature (~21-22°C) and salinity (20-25 ppt) before being allocated to experimental treatments. The majority ofmedusae were used in heat tolerance experiments, which ran for 96 hours at temperatures between 22°C-32°C. Significant mortality of G. vertens from all locations occurred when temperatures met or exceeded 28°C for 72h, suggesting that G. vertens \u27thermal tolerance is 28°C and that populations in the field are at least partially controlled by water temperatures. Understanding the thermal decline in areas where predatory species are not present is critical for managing public awareness of this hazard. Monitoring of high human use areas for thermal minimums can reduce potential encounters with this highly venomous species. In Barnegat Bay, for instance, water temperatures may exceed 28°C by the end of June into the beginning of July, which was confirmed by deploying temperature recorders. Predation experiments were also conducted to confirm that Chrysaora chesapeakei is a predator of G. vertens and to determine the bell diameter ratio at which they could be killed or consumed. C. chesapeakei is indeed capable of killing G. vertens, even at ratios of 1.19:1, and partially or completely consumed G. vertens when bell ratios approached 1.67:1. Therefore, it seems that C. chesapeakei likely also plays a role in the decline of G. vertens populations in Barnegat Bay, which decline throughout the month of July. Lastly, G. vertens medusae were sent to the Cornell Isotope Laboratory along with samples of potential prey items and plants from the same areas in which the medusae were collected for Stable Isotope Analysis (SIA). The δ15N and δ13C data obtained from SIA were plotted to determine the trophic position of these organismal groups, which confirmed that amphipods and copepods are likely very important prey items for G. vertens

Probing Individual Star Forming Regions Within Strongly Lensed Galaxies at z > 1

Star formation occurs on physical scales corresponding to individual star forming regions, typically of order ~100 parsecs in size, but current observational facilities cannot resolve these scales within field galaxies beyond the local universe. However, the magnification from strong gravitational lensing allows us to measure the properties of these discrete star forming regions within galaxies in the distant universe. New results from multi-wavelength spectroscopic studies of a sample of extremely bright, highly magnified lensed galaxies are revealing the complexity of star formation on sub-galaxy scales during the era of peak star formation in the universe. We find a wide range of properties in the rest-frame UV spectra of individual galaxies, as well as in spectra that originate from different star forming regions within the same galaxy. Large variations in the strengths and velocity structure of Lyman-alpha and strong P Cygni lines such as C IV, and MgII provide new insights into the astrophysical relationships between extremely massive stars, the elemental abundances and physical properties of the nebular gas those stars ionize, and the galactic-scale outflows they power.Comment: 4 pages, 3 figures. To be published in the Proceedings of IAU Symposium 309. For more details and closely related work see also arXiv:1310.6695 and arXiv:1406.335

A re-examination of the growth of the gummy shark (Mustelus antarcticus) from Queensland, Australia

The gummy shark (Mustelus antarcticus) is endemic to Australia and is the target of commercial fisheries in southern Australia. However, the Queensland population is subjected to low levels of fishing mortality. The present study re-analysed a limited length-at-age dataset collected from central Queensland to estimate growth parameters in a Bayesian framework, with informative priors for size-at-birth and maximum size. Growth parameters were estimated using a multi-model approach. This study showed that M. antarcticus caught in Queensland exhibits slow growth compared with conspecifics in southern Australia, and females grow slower and larger than do males. The combined length-at-age data for males and females was best described by the von Bertalanffy growth function and the growth parameters were L∞ = 1852 mm (total length, TL), L0 = 261 mm TL and k = 0.044 year−1 for males and females combined. The ‘BayesGrowth’ R package offers a simple method to minimise bias in the estimation of growth parameters from a limited length-at-age dataset in a Bayesian framework

A re-examination of the growth of the gummy shark (Mustelus antarcticus) from Queensland, Australia

The gummy shark (Mustelus antarcticus) is endemic to Australia and is the target of commercial fisheries in southern Australia. However, the Queensland population is subjected to low levels of fishing mortality. The present study re-analysed a limited length-at-age dataset collected from central Queensland to estimate growth parameters in a Bayesian framework, with informative priors for size-at-birth and maximum size. Growth parameters were estimated using a multi-model approach. This study showed that M. antarcticus caught in Queensland exhibits slow growth compared with conspecifics in southern Australia, and females grow slower and larger than do males. The combined length-at-age data for males and females was best described by the von Bertalanffy growth function and the growth parameters were L∞ = 1852 mm (total length, TL), L0 = 261 mm TL and k = 0.044 year−1 for males and females combined. The ‘BayesGrowth’ R package offers a simple method to minimise bias in the estimation of growth parameters from a limited length-at-age dataset in a Bayesian framework

Inversion of long-lived trace gas emissions using combined Eulerian and Lagrangian chemical transport models

Supplement related to this article is available online at: http://www.atmos-chem-phys.net/11/9887/2011/acp-11-9887-2011-supplement.zip.We present a method for estimating emissions of long-lived trace gases from a sparse global network of high-frequency observatories, using both a global Eulerian chemical transport model and Lagrangian particle dispersion model. Emissions are derived in a single step after determining sensitivities of the observations to initial conditions, the high-resolution emissions field close to observation points, and larger regions further from the measurements. This method has the several advantages over inversions using one type of model alone, in that: high-resolution simulations can be carried out in limited domains close to the measurement sites, with lower resolution being used further from them; the influence of errors due to aggregation of emissions close to the measurement sites can be minimized; assumptions about boundary conditions to the Lagrangian model do not need to be made, since the entire emissions field is estimated; any combination of appropriate models can be used, with no code modification. Because the sensitivity to the entire emissions field is derived, the estimation can be carried out using traditional statistical methods without the need for multiple steps in the inversion. We demonstrate the utility of this approach by determining global SF6 emissions using measurements from the Advanced Global Atmospheric Gases Experiment (AGAGE) between 2007 and 2009. The global total and large-scale patterns of the derived emissions agree well with previous studies, whilst allowing emissions to be determined at higher resolution than has previously been possible, and improving the agreement between the modeled and observed mole fractions at some sites

Spatially Resolved Galactic Wind in Lensed Galaxy RCSGA 032727-132609

We probe the spatial distribution of outflowing gas along four lines of sight separated by up to 6 kpc in a gravitationally-lensed star-forming galaxy at z=1.70. Using MgII and FeII emission and absorption as tracers, we find that the clumps of star formation are driving galactic outflows with velocities of -170 to -250 km/sec. The velocities of MgII emission are redshifted with respect to the systemic velocities of the galaxy, consistent with being back-scattered. By contrast, the FeII fluorescent emission lines are either slightly blueshifted or at the systemic velocity of the galaxy. Taken together, the velocity structure of the MgII and FeII emission is consistent with arising through scattering in galactic winds. Assuming a thin shell geometry for the out owing gas, the estimated masses carried out by these outfows are large (> 30 - 50 $\rm{M_{\odot} yr^{-1}}$), with mass loading factors several times the star-formation rate. Almost 20% to 50% of the blueshifted absorption probably escapes the gravitational potential of the galaxy. In this galaxy, the outflow is "locally sourced", that is, the properties of the outflow in each line of sight are dominated by the properties of the nearest clump of star formation; the wind is not global to the galaxy. The mass outflow rates and the momentum flux carried out by outflows in individual star forming knots of this object are comparable to that of starburst galaxies in the local Universe.Comment: 19 pages, 10 figure, accepted for publication in MNRA

Joint inference of CFC lifetimes and banks suggests previously unidentified emissions:Nature Communications

AbstractChlorofluorocarbons (CFCs) are harmful ozone depleting substances and greenhouse gases. CFC production was phased-out under the Montreal Protocol, however recent studies suggest new and unexpected emissions of CFC-11. Quantifying CFC emissions requires accurate estimates of both atmospheric lifetimes and ongoing emissions from old equipment (i.e. ‘banks’). In a Bayesian framework we simultaneously infer lifetimes, banks and emissions of CFC-11, 12 and 113 using available constraints. We find lifetimes of all three gases are likely shorter than currently recommended values, suggesting that best estimates of inferred emissions are larger than recent evaluations. Our analysis indicates that bank emissions are decreasing faster than total emissions, and we estimate new, unexpected emissions during 2014-2016 were 23.2, 18.3, and 7.8 Gg/yr for CFC-11, 12 and 113, respectively. While recent studies have focused on unexpected CFC-11 emissions, our results call for further investigation of potential sources of emissions of CFC-12 and CFC-113, along with CFC-11.</jats:p